Good question, Brutus - but I think Caesar's forgiveness is psychologically acute on several fronts. First, however his ambitions colored his actions, I do believe that it was perfectly in character to chew Vorenus out severely, then dismiss him without further action. A Primus Pilus, and evocati to boot, was not the kind of leader that even Caesar would dismiss (he's said to have loved his centurions above any soldiers in the army). Second, I think he was more upset by the possibility of disloyalty than the action Vorenus actually took, and the way Vorenus played the scene, it was clear he had divided thoughts but was loyal to Caesar. If Caesar punished everyone in his army who was ambivalent about the actions he was taking, he'd lose half of it. Thirdly, I DO believe the lines where Caesar said that powerful gods were behind Vorenus and Pullo - there's nothing to indicate that Caesar did not believe in the gods, however strongly he followed his own road. Perhaps that comment strikes as historically true as anything in the scene. And fourthly - to punish a man of Vorenus' achievement in the army would be bad for morale without a reason, and he certainly wouldn't want it known that Vorenus had Pompey in his hand and let him go!

So on the whole I'd say - yes, in this case, it is historically accurate. Caesar and other commanders were savage about disloyalty, but this wasn't really a case of disloyalty as much as split loyalty. And Caesar showed himself remarkably clement with Romans of divided loyalties.